Hybrid density functional studies of native defects and H impurities in wurtzite CdSe

Abstract

In this study, the formation energies and electronic properties of six native defects as well as H impurities in wurtzite (wz) CdSe are systematically investigated using hybrid density functional calculations. It is shown that native defects, including antisite Cd_Se and interstitial Cd_i, may be sources of the unintentional n-type conductivity in CdSe under Se-poor conditions; meanwhile, the vacancy defect V_Se is not a good donor. However, when the common H impurity is considered, it is suggested that both the substitutional impurity H_Se and the interstitial impurity H_i are the dominant and effective origins of the unintentional n-type conductivity in Se-poor conditions. However, unintentional p-type conductivity in CdSe is challenging to form regardless of the growth conditions. Moreover, hybrid functional calculations of the electronic structures show that the six native point defects and the extrinsic impurities H_i and H_Se will cause more or fewer changes in the band gap. Among all considered defects and impurities, it is found that only the interstitial defect Cd_i introduces impurity levels into the band gap. In particular, the present hybrid functional calculations theoretically affirm that the vacancy defect V_Cd in CdSe can induce a 2 μ_B magnetic moment; however, other native defects will not introduce any magnetic moment.